Abstract: A zonal beamsplitter for use with surgical microscopes including a pair of right triangular prisms positioned adjacent to each other in opposing relation along substantially planar surfaces defining their respective hypotenuses. The planar surface of one prism is bi-zonal and includes a first zone for diverting substantially all of a portion of an image-quality optical signal at an angle from the direction of travel of the optical signal, and a second zone for conducting substantially all of the remaining image-quality optical signal therethrough. The plane of the first zone may be offset from that of the second zone and/or coated with an opaque reflective surface such as a metal foil.